1. Field of the Invention
The present invention relates to a brushless motor for rotating an optical disc, a magneto-optical disc or the like.
2. Description of the Related Art
Disk devices equipped with head mechanisms for reading information recorded on a disk or writing information to a disk are known in the form of devices for optical disks including CDs, DVDs and MDs, and for magneto-optical disks. In such disk devices, outer-rotor type brushless motors are used as so-called spindle motors that drive the disc in rotation.
When the disk device is used, it is necessary to load and unload a disk on a turntable that is united with the rotor of the spindle motor, and when the disc is removed from the turntable, a force is applied in the direction that would cause the rotor to come off the bearing. Consequently, the spindle motor requires a mechanism that prevents the rotor from coming off the bearing.
In response to such needs, a spindle motor of this sort, which is shown in FIG. 11, was disclosed in Japanese Patent Laid-Open Publication No. H11-55898. This spindle motor comprises a rotor having a drive magnet 108 at the inside of a rotor case 107, and a stator core 106 on which a coil is wound, and which is arranged facing the drive magnet 108. A washer 104 having a hole that is smaller than the outer diameter of a rotary shaft 101 is fixed in place at the end of a bearing 102 by a cap 105, which is held in a bearing housing 103, and a slit 101a is provided in the portion of the rotary shaft 101 that passes through the washer 104.
With the spindle motor in FIG. 11, if the rotor 107 moves in the direction that is upwards in FIG. 11 when the disc is removed, the inner diameter portion of the washer 104 strikes the stepped portion where the slit 101a is provided in the rotational shaft 101, whereby the rotor 107 can be prevented from coming off the stator. Furthermore, with the spindle motor in FIG. 11, oil within the bearing is prevented from flying out by way of a labyrinth seal formed by the slit 101a in the rotational shaft 101 and the washer 104.
However, with the motor in FIG. 11, because the mechanism that prevents the rotor from coming off and the mechanism that prevents the oil from flying out necessitate the washer 104 and the cap 105, the number of parts is increased, which is a problem in that manufacturing costs are increased.